The helicopter, a MH-53E Sea Dragon, was on a routine training mission, the Navy said. The cause of the unarmed transport helicopter's crash is under investigation.

The helicopter went down in the Atlantic Ocean 20 miles off the Virginia coast, the U.S. Coast Guard said. Two Navy aircrews hoisted four people from the water and transported them to Sentara Norfolk General Hospital. Extent of injuries for the three survivors is not known, the Navy said. Their names were not released.

The Coast Guard said it received a call at approximately 11 a.m. reporting the Sea Dragon had crashed and that another Navy aircrew had dropped a life raft to the people in the water.

Petty Officer David Weydert told Yahoo News two Coast Guard ships went to the scene, and one was between 2 and 3 nautical miles from the crash area. Helicopters from the U.S. Navy as well as the U.S. Coast Guard Cutter Shearwater are participating in the search, Weydert said.

The incident comes a day after four people were killed in a U.S. Air Force helicopter crash off the coast of Norfolk, England, during a "low-level" training exercise. There were no survivors of that crash.